3D printed composites - Benchmarking the state-of-the-art

Fused filament fabrication (FFF) is a 3D printing technique which allows layer-by-layer build-up of a part by the deposition of thermoplastic material through a nozzle. The technique allows for complex shapes to be made with a degree of design freedom unachievable with traditional manufacturing methods. However, the mechanical properties of the thermoplastic materials used are low compared to common engineering materials. In this work, improved 3D printing feedstocks for FFF, with carbon fibres embedded in a thermoplastic matrix to reinforce the material, are investigated. The state-of-the-art in composite 3D printing is reviewed and the capabilities of two different commercially available composite printing methods are assessed by print trials, optical microscopy and mechanical characterization of the printed materials. It is found that printing of continuous carbon fibres using the MarkOne gives significant increases in performance over unreinforced thermoplastics, with mechanical properties in the same order of magnitude of typical unidirectional epoxy matrix composites. The method, however, is limited in design freedom as the brittle continuous carbon fibres cannot be deposited freely through small steering radii and sharp angles. Filaments with embedded carbon microfibres (∼;100 μm) show better print capabilities and are suitable with standard printing methods, but only offer a slight increase in mechanical properties over the pure thermoplastic properties.